The Dengue virus (DEN), is a coated virus whose lipid membrane contains two of its three structural proteins: the envelope protein (E) and the membrane protein (M). The E protein covers an icosaedric nucleocapsid composed by the third of its structural proteins, the core protein. This virus belongs to the Flaviviridae family and four different serotypes exist. Its transmission to the man is carried out through the mosquito Aedes aegypti that belongs to the Stegomia family. The disease produced in the human for this virus was considered as benign and was described as Dengue Fever or Classical Dengue (DF) until the appearance of a more serious modality and sometimes lethal, characterized by hemorrhagic fever and shock, denominated: Hemorrhagic Dengue Fever and Dengue Shock Syndrome (HDF/DSS) (Hammon WMc. New hemorrhagic fever in children in the Philippines and Thailand. Trans Assoc Physicians 1960; 73: 140–155). Several epidemiological studies have been carried out evidencing as a risk factor the sequential infection of two different viral serotypes (Kouri G P, Guzman M G, Brave J R. Why dengue hemorrhagic fever in Cuba) 2. An integral analysis. Trans Roy Soc Trop Med Hyg 1987; 72: 821–823). This phenomenon is explained by the immuno-enhancement, which is based on an increase of the viral infection by increasing the entrance of the virus-antibody complex to the cell through the Fc receptors of the target cell (monocytes) (haistead SB. Pathogenesis of dengue: challenges to molecular biology. Science 1988; 239: 476–481).
Different technologies have been developed to produce live attenuated vaccines, but at present there exist multiple unsolved issues on the possible benefits of these vaccines, since they could revert to the virulence, viral interference and inter-genomic recombination. Alternately, recombinant antigens can be obtained as possible components of a subunit vaccine (Feighny, R., Borrous, J. and Putnak R. Dengue type-2 virus envelope protein made using recombinant baculovirus protects mice against virus challenge. Am. J. Trop. Med. Hyg. 1994. 50(3). 322–328; Deubel, V., Staropoli, I., Megret, F., et al. Affinity-purified dengue-2 virus envelope glycoprotein induces neutralizing antibodies and protective immunity in mice. Vaccine. 1997. 15, 1946–1954).
The main antigen of the virus is the envelope protein DENe. This protein is the major component of the viral surface and is thought to mediate the binding of the virus to the cellular receptor (A Heinz F X, Berge R, Tuma W et al. A topological and functional model of epitopes on the structural glycoprotein of tick-borne encephalitis virus defined by monoclonal antibodies. Virology. 1983; 126: 525). This protein has structural homology with that of the tick borne encephalitis virus (TBE) (Rey, F. A., Heinz, F. X., Mandl, C., et al. The envelope glycoprotein from tick borne encephalitis virus at 2 A° resolution. Nature 1995; 375: 291–298) and it is also structurally conserved among serotypes.
The insect cells constitute one of the systems most used for the expression of diverse heterologous genes that employ the baculovirus system as vectors. These vectors have been used for the expression of several combinations of structural and nonstructural proteins of the Encephalitis Japanese virus (JEV), DEN-1, DEN-2 and DEN4, (Matsuura Y, Miyamoto M, Soto T et al. Characterization of japanese encephalitis virus envelope protein expressed by recombinant baculoviruses. Virology 1989; 173: 677–682; Deubel V, Bordier M, Megret F et al. Processing, secretion and immunoreactivity of carboxy terminally truncated dengue-2 envelope proteins expressed in insect cell by recombinant baculoviruses. Virology 1991; 180: 440–447; Putnak R, Feighny R, Burrous J et al. Dengue 1 virus envelope glycoprotein gene expressed in recombinant baculovirus elicit virus neutralization antibodies in mice and protects them from virus challenge. Am J Trop Med Hyg 1991; 45: 159–167; Feighny R, Burrous J, Putnak R. Dengue type 2 virus envelope protein made using recombinant baculovirus protects mice against virus challenge. Am J Trop Med Hyg 1994; 50: 322–328). Another system used has been the cells of Drosophila melanogaster expressing different variants of the E protein (PCT/US96/07627). In spite of obtaining an appropriate functional response, upon using the proteins expressed in these systems, they imply a high cost for the development of scale-up production processes; therefore, the expression in yeast has been an alternative to produce recombinant structural proteins of flavivirus. However, in the case of the DENe protein, expressed in Pichia pastoris (PCT/US96/07627; Sugrue R. J., Fu H., Howe J., Chan Y. Expression of the Dengue virus structural proteins in Pichia pastoris leads to the generation of virus-like particles. J. Virol. 1997. 78, 1861–1866), the levels of expression are low, either secreted or intracellularly, hindering the purification process.
In parallel, several variants of the DENe protein have been obtained in bacteria. One of them was the C-terminal portion of the E protein of the JEV fused to a protein of the Tryptophan metabolism (TrpE) of E. coli. This protein was produced as inclusion bodies and was recognized by neutralizing monoclonal antibodies (Mabs) using immunodetection techniques. However, pure preparations of this protein were unable to develop neutralizing antibodies and to protect against viral challenge (Mason P. W., Zogel M. V., Semproni A. R., et al. The antigenic structure of dengue type I virus envelope and NS1 protein expressed in E. coli. J Gen Virol. 1990. 71: 2107–2114). In addition, another construction was made (Srivastava A. K., Morita K., Matsuo S., et al. Japanese encephalitis virus fusion protein with protein A expressed in E. coli confers protection in mice. Microbiol Immunol. 1991. 35: 863–870), that contains the protein A of Staphylococcus aurius fused to the C-terminal fragment of the E protein, followed by the N-terminal segment of the nonstructural protein of the JEV, the NS1. In this case the fused protein was soluble, facilitating its purification by affinity chromatography. Upon immunizing mice with this pure protein high neutralizing antibodies titers were obtained, which also inhibited haemagglutination and protected against the viral challenge with the JEV. Similar results were obtained using the DENe region of the DEN-2 fused to the protein A of S. aureus (Srivastava A. K., Putnak R. J., Warren R. L., Hoke C. H. Mice immunized with a dengue type 2 virus E and NS1 fusion protein made in Escherichia coli are protected against lethal dengue virus infection. Vaccine. 1995. 13: 1251–1258); however, it is not possible to use these preparations in humans due to the presence of the protein A, which has shown a high affinity for the human immunoglobulin G (IgG).
Finally, it has been reported a fusion protein that contains the B domain of the DENe protein of DEN-2 and the maltose binding protein (MBP) of E. coli (Simmons M., Nelson W. M., Wu S. J., Hayes C. G. Evaluation of the protective efficacy of a recombinant dengue envelope B domain fusion protein against dengue 2 virus infection in mice. Am J Trop Med Hyg. 1998. 58: 655-662) denominated MBP-DomB. This protein variant was immunogenic in mice and elicited neutralizing antibodies.